It is now relatively common to incorporate lightweight particles into relatively high density slurried granulate materials which are then formed and dehydrated into objects such as boards, moldings and the like. To the many desirable characteristics of the granulate, such as good thermal and acoustic insulating characteristics, fire-resistance and low cost, the further advantage of a reduced weight is added to facilitate the handling of the granulate and reduce transportation costs.
In the past it has been common to incorporate polystyrene foam particles into a slurry of a granulate, such as gypsum, concrete or mortar for example, and a liquid, usually water. The slurry is then agitated to evenly distribute the foam particles throughout the slurry. However, as soon as agitation ceases the buoyancy of the low-density foamed particles floats the particles to the slurry top. This prevents the formation of an even slurry-foamed particle mixture, particularly since it usually takes several hours or days to dehydrate the slurry and dry the granulate into solid objects. During that period the foamed particles invariably float to the top of the slurry or at least tend to concentrate in the upper region thereof.
Foamed polystyrene beads have become widely accepted for mixing with granulates because of their fire-resistancy, an essential for building materials, and their low cost. Such beads usually have sizes ranging from between about 3 to about 10 millimeters in diameter. The bead size is too great for direct incorporation in the granulates since such large beads would noticeably weaken the hardened granulate. Consequently, the beads were reduced in size by cutting them with sharp blades or knives. The cuts were clean and essentially planar and damaged a minimum number of the foamed bead cells. Heretofore this was assumed to be desirable, giving the cut beads a generally neat and clean appearance. As will become more apparent hereinafter this contributed heavily to the problems encountered in attempts to evenly distribute such foamed particles in the slurry to decrease the density of the finally dehydrated granulate.